I only have the Guten and never used the Robobrew before, so not really a comparison as such.
We've done around 10 brews in the Guten so far and it has been great. Electronic temperature control trumps gas any day IMO as long as you are willing to wait the extra heat up time.
Had no real issues with it, as is always the case with Chinese stuff, the interface is always lacking. The control faceplate is tricky to use and confusing, but it's probably the same for the Robobrew.
Construction seems relatively robust to me although I've not seen a GF in person to compare it to, I'm not worried about many of the components except that the lip where the false screen sits always worries me (it is just needlessly small and thin, I don't really understand why, it would cost nothing to make that lip bigger). People get worried about how thin the false screen itself is but steel is a lot tougher than people give it credit for and that mesh is fine IMO, sure other manufacturers might use thicker mesh but it doesn't bother me.
The only other things that worry me is the circuit board (the fabrication of the Guten circuit board is a lot better than the Robobrew purportedly), how long that will last, potential water ingress into the control box (seal failure), and the longevity of the pump. These things will only become apparent after a couple years I would imagine.